1. Field of the Invention
The present invention relates to an image forming apparatus, which is applied to a printing machine, such as an inkjet printer, and forms images by injecting ink drops onto a printing paper fed on a feeding path.
2. Description of Related Art
Among conventional inkjet printers, there is a full-line type inkjet printer by which printing is done only with a secondary sweeping in which a printing paper is fed along a feeding direction (Patent document 1: Japanese Patent Application Laid-Open No. 2002-154196). In such a full-line type inkjet printer, printing of one entire line of text onto the paper is successively executed.
Recently, various requirements are made to a printer, such as handling of higher pixelated printing images, further multifunctional capability, further downsizing and so on. To meet the requirements, it is needed to locate highly condensed ink heads closely each other. If unnecessary ink drops (mists) are made other than main ink drops injected from an ink head, the mists can't reach to a printing sheet because of their relatively small mass and low speed. Then the mists float in the air and then may directly attach on other ink heads or a head holder. As a result, injection ports on the ink heads are occluded and then injection failures may occur, such as absence of injected ink and lack of injected ink amount. In addition, if the inks attaching and then growing within the printer drop off onto a fed paper or a feeding belt due to self-weight thereof, printed matters may become tainted.
To solve the above problems, a technique is proposed in the Patent Document 1. According to the technique, the mists are prevented from attaching onto the other ink heads or the head holder by securing a predetermined distance or more between the ink heads adjacent in a feeding direction.
However, according to the technique in the Patent Document 1, the printer must ensure length in the feeding direction and then the printer itself may become large. In addition, the mists may infiltrate into the inside of the printer and attach onto other functional components due to the distance secured between the highly condensed ink heads and thereby unexpected negative effects may occur.